html,
body {
    width: 100%;
    height: 100%;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
}

button {
    padding: 0;
    border: 0;
    outline: none;
}

.plane {
    width: 100%;
    height: 100%;
    max-width: 420px;
    max-height: 720px;
    background: url(../images/startgame.png) no-repeat 0 0/100% 100%;
    position: relative;
    overflow: hidden;
}


/* 开始游戏按钮 */

.begin {
    width: 160px;
    height: 50px;
    border-radius: 16px;
    background-color: #ddd;
    border-bottom: 2px solid #666;
    position: absolute;
    left: calc(50% - 70px);
    bottom: 30px;
}

.begin:active {
    height: 47px;
    border: 0;
}

.game {
    width: 100%;
    height: 100%;
    display: none;
    /*默认隐藏*/
    position: absolute;
    left: 0;
    top: 0;
    z-index: 9;
}

.bg {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background: url(../images/bg.jpg) no-repeat 0 0/100% 100%;
}

.bg2 {
    top: -720px;
}


/* 我方飞机 */

.myplane {
    width: 60px;
    height: 72px;
    background: url(../images/me.gif) no-repeat 0 0/100% 100%;
    position: absolute;
    left: calc(50% - 30px);
    top: 680px;
}

img {
    position: absolute;
    z-index: 99;
}